Customs question: Kigali to Nairobi; separately ticketed flight to Germany from Nairobi

I have contacted Rwanda airlines and it said that I will not need to clear customs/immigration and go through security in NBO to connect to my flight, which was bought separately, to Frankfurt, Germany. Kenya airlines has told me two different thing. Internet in general says I will need to go through customs and security again because that flight was purchased separately. There are not a lot of good flight options between KGL and NBO, and one flight leaves me with 2 hours and 40 minutes before the long haul flight to Germany. Is this enough time? Have people who have flown this route (KGL to NBO) had to go through security and immigration to catch their next international flight? I really don't want to miss the long haul flight...thanks!